Low-capacitance PbTe photodiodes

Abstract

Thin-film PbTe photodiodes have been operated at 80 K with significantly reduced capacitance. The technique is based upon limitation of the voltage-induced change of the depletion-layer volume by the presence of an insulating substrate. Capacitances as low as 64 pF for a 9-mil-square diode and 35 pF for a 28-mil-square diode have been achieved with retention of background-limited detectivities, which were typically about 1.7×1011 cm Hz1/2 W−1 for peak wavelength near 5 μm.